/shader-dev <request>

shader-dev/
├── SKILL.md                      # Core skill (this file)
├── techniques/                   # Implementation guides (read per routing table)
│   ├── ray-marching.md           # Sphere tracing with SDF
│   ├── sdf-3d.md                 # 3D signed distance functions
│   ├── lighting-model.md         # PBR, Phong, toon shading
│   ├── procedural-noise.md       # Perlin, Simplex, FBM
│   └── ...                       # 34 more technique files
└── reference/                    # Detailed guides (read as needed)
    ├── ray-marching.md           # Math derivations & advanced patterns
    ├── sdf-3d.md                 # Extended SDF theory
    ├── lighting-model.md         # Lighting math deep-dive
    ├── procedural-noise.md       # Noise function theory
    └── ...                       # 34 more reference files

// WRONG
vec2 uv = (2.0 * fragCoord - iResolution.xy) / iResolution.y;
// CORRECT
vec2 uv = (2.0 * gl_FragCoord.xy - iResolution.xy) / iResolution.y;

void mainImage(out vec4 fragColor, in vec2 fragCoord) {
    // shader code...
    fragColor = vec4(col, 1.0);
}

void main() {
    mainImage(fragColor, gl_FragCoord.xy);
}

// WRONG — getAtmosphere() calls getSunDirection() before it's defined
vec3 getAtmosphere(vec3 dir) { return getSunDirection(); } // Error!
vec3 getSunDirection() { return normalize(vec3(1.0)); }

// CORRECT — define callee first
vec3 getSunDirection() { return normalize(vec3(1.0)); }
vec3 getAtmosphere(vec3 dir) { return getSunDirection(); } // Works

// WRONG
#define SUN_DIR normalize(vec3(0.8, 0.4, -0.6))

// CORRECT
const vec3 SUN_DIR = vec3(0.756, 0.378, -0.567); // Pre-computed normalized value

const fs = document.getElementById('fs').text.trim();

// 1. State variables FIRST
let frameCount = 0;
let startTime = Date.now();

// 2. Canvas/GL init, shader compile, FBO creation
const canvas = document.getElementById('canvas');
const gl = canvas.getContext('webgl2');
// ...

// 3. Functions and event bindings LAST
function resize() { /* can now safely reference frameCount */ }
function render() { /* ... */ }
window.addEventListener('resize', resize);